Development of Novel Multifunctional Cosmetic Raw Materials and Their Applications. III. Effect of Random Copolymer of Polyoxyethylene/polyoxypropylene on Self-organizing Structures of Nonionic Surfactants

Abstract

In this study, the effect of polyoxyethylene (POE)/polyoxypropylene (POP) dimethylethers [EPDMEs] with various molecular weights and polarities on self-organizing structures of pentaethyleneglycol dodecylether (C12E5) was investigated. The investigation on micelle formation of C12E5 in EPDME aqueous solutions showed that [1] EPDME disturbed the micelle formation of C12E5, [2] the micelle formation was also disturbed more strongly with the increase of temperature, and [3] the surface tension of solution became low in spite of the decrease of the amount of adsorption of C12E5 with the increase of the concentration of EPDME. The result of measuring the cloud points of C12E5 in EPDME solutions unveiled that the cloud points became remarkably higher at high EPDME concentration, suggesting that the rise of the cloud points in EPDME solutions might be caused by the decrease of the aggregation number of C12E5. Moreover, it was speculated that C12E5 and EPDME might aggregate partially and form mixed micelles, since the cloud points of their mixture appeared beyond 50 °C. Liquid paraffin could be solubilized at a specific temperature above the could point of C12E5 in 27wt% EPDME (17/4) aqueous solution. It was speculated that [1] a special micelle containing oil might be formed when the cohesive force of the hydrophobic groups of C12E5 increased by solubilizing liquid paraffin, [2] EPDME distributed to the hydrophilic chain of C12E5, and [3] the curvature of the interfacial film became positive. Therefore, as described in the previous study, EPDME functions as a hydrophilic co-surfactant when the concentrations of both EPDME and polyoxyethylene nonionic surfactants are high, because EPDME may probably distribute on the polyoxyethylene chain of the surfactant. A microemulsion can be formed in a wide temperature range by preventing the aggregation of nonionic surfactants with the increase of temperature. © 2006, Japan Oil Chemists' Society. All rights reserved.